Hitherto, as a light-emitting diode (LED) that emits infrared light, or red, orange, yellow, or yellow-green visible light, a compound semiconductor LED has been known which is provided with a light-emitting layer composed of aluminum, gallium and indium phosphide (with empirical formulas of (AlXGa1-X)YIn1-YP; 0≦X≦1, 0<Y≦1), AlXGa1-XAs(0≦X≦1), or InXGa1-XAs(0≦X≦1). In such an LED, a light-emitting portion provided with the light-emitting layer composed of (AlXGa1-X)YIn1-YP (0≦X≦1, 0<Y≦1) is formed on a substrate material, such as gallium arsenide (GaAs) which is, in general, optically opaque to light emitted from the light-emitting layer and is also not very strong mechanically.
Therefore, in recent years, in order to produce a light-emitting diode with higher luminance and higher output, technologies have been disclosed in which the GaAs substrate material is removed, and then an GaP substrate that is capable of transmitting light emitted is joined, and an inclined surface is formed on a side surface so as to constitute a light-emitting diode increased in the luminance (refer to, for example, PTL 1 to 5).